Color photographs



Patented June I, 1943 UNlTED STATES PATENT OFFICE CQLOR PHOTOGRAPHS John Eggert, Leipzig-Gohlis, and Bruno 'Wendt,

Dessau, Germany; assignors, by mesne assignments, to General'Aniline & Film Corporation, New York, N. Y., a corporation of Delaware 1% Drawing. Application- June 13, 1938, Serial No. 213,427. In Germany June 22, 1935 11 Claims. (e1. 95-2) Our present invention relates to the production of color photographs by the reversal process. In application Ser. No. 85,848, filed June 18,

. 1936, now U. S. Patent No. 2,153,617 of April 11,

1939, of which the present application is a con-.

tinu'ation in part, we have disclosed a method of producing color pictures by the employment of a color. photographic multi-layer material, in which the individual light-sensitive silver halide emulsion layers are separated byfilter layers, the

dyestufis of which are stable against the normal photographic treating baths, i. e., the developers, fixing baths and silver-removing-baths.

The method described in our parent applica tion consists in taking a picture on said photo-. graphic material, developing and fixing, reducing the silver formed to undevelopable silver halide, differentially exposing the individual layers to monochromatic light by means of the colored filter layers, whereby a color separation capable of development is formed in each of the individual layers. developing the color separations one after the other in color or otherwise imparting color thereto, and removing the dyestuffs in the filter layers after the formation of at least one color picture.

It is an object of our present invention to provide a' modification of our process as disclosed in our parent application Ser. No. 85,848, which will yield direct positives by the reversal method.

Further objects will become apparent from the detailed description following hereinafter.

We have found that the process can advantage-ously be used for the production of reversal pictures if there is used a number of superimposed silver halide emulsion layers separated by a color-filter layeror layers resistant to photographic treating baths and the silver halide images remaining after the silver images produced by the first development have been dis- The further treatment consists in solved out are again separately exposed with the aid of the filter layers, the filter dyestuffs being bleached only after the production of at least one dyestufi component image.

' .As exposure material a bipack is preferred which has on one support two differently sensitive silver halide emulsion layers separated by a color-filter layer resistant to photographic treating baths and on the other support a. single silver halide emulsion layer sensitive to the rest of the visible spectrum. The silver halide images remaining in the two layers superimposed on one support after the silver images produced by the first development have been dissolved out are again separately exposed with the aid of the filter layer, and the filter dyestufi is only bleached after the production of at least one dyestuff component image.

The following bipack material, for example, is suitable: I

On one support is a blue-sensitive layer on which is a, color filter layer which contains the azo-dyestufi from diazotized ortho-chloraniline and l-(sulfophenyl) -5-pyrazolone-3-carboxylic acid-ethyl ester (with calcium acetate as fixing agent); on the filter layer is a green-sensitive layer. Another support carries a red-sensitive layer which may be coated with a yellow or red capable of development, while the green-sensitive layer is unaffected. In the blue-sensitive layer ayellow picture is developed with a yellowdeveloper described in U. S. patent application Ser. No. 82,930, filed June 1, 1936, whereupon the color-filter layer is bleached by treatment with a solution containing sodium hydrosulfite and sodium carbonate. Other suitable hydrosule fite solutions are described in Eder, Jahrbuch fiir Photographie, 1905, page 28, and Photo graphische Korrespondenz," 1908, page 406. The yellow image dyestuff and the silver halide of the green-sensitive layer are not attacked by this treatment. The silver produced by the development can be dissolved out immediately or with the silver of the other layer. After exposure the green-sensitive layer is developed with a purple-developer, which contains, for example, diethyl-para-phenylenediamine and an iso-oxazolone, To a purple picture and the silver or this purple images- The red-sensitive single layer ofthe bipack is developed either to a negative or by the reversal process to a positive. The image of the single layer can :be developed either in black-and-white or in color, forexample to blue-green with a color developer containing 1-hydroxy-4-methoxynaphthalin, or the black-and-white developed picture can be dyed or toned by a known process.

The three layers sensitive to different regions parent application, Ser. No. 85,848, a second yellow or red filter. layer is necessary between the greenand red-sensitive layers. When the three layers are carried on one support alllthree component images mustbe converted into color images. The three layers can be arranged in the known manner on one or both sides of the support. If the three layers are arranged on one side the blue-green picture can, for example be developed by using indoxyl or an indoxyl derivative to an. image of the class of indigo dyestuffs. If the red-sensitive layers is on the back of the support the blue-green picture can'be produced by iron-blue toning on one side. If the filter'is bleached by hydrosulfite or an equivalently operating body, dyestufis of the indigo class are partly reduced to the leuco compounds, When the film is later brought into contact with the air automatic i e-oxidation to the dyestuif occurs. I

What we claim is: a.

1. A process of producing color photographs by the reversal method, which process comprises exposing to light controlled by an object to be photographed a multi-layer material comprising a support, a plurality of silver halide emulsion layers sensitive to three distinct regions of the visible spectrum, said silver halide emulsion layers being separated by at least one colored filter layer comprising azo dyestuiI derived from a diazotized arylamine and a pyrazolene, said dyestufi being resistant to the photographic treating baths necessary for converting a latent silver image .into a positive dyestufi image, but capable of being decolorized by a weak solution capable of destroying the color-developed dyestufis and of acting on silver halide, developing the latent images formed by exposure with an ordinary photographic developer, removing the silver-images by means of a chemical solvent for silver, separately exposing at least one of. the residual silverhalide images to monochroby the reversal method, which process comprises exposing to light controlled by an object to be photographed a bi-pack comprising a support, a blue-sensitive silver halide emulsion layer on ,said support, a filter layer superposed on said layer containing a yellow dyestufl resistant to the photographic treating baths necessary for converting a latent silver image into a positive dyestuil image, but capable of being decolorized of sodium hydrosulfite, said solution being inby a weak solutionof sodium hydrosulfite and sodium carbonate, said solution being incapable of destroying the color-developed dyestuffs and of acting on silver halide, a green-sensitive silver halide emulsion on said filter layer, a second support having cast thereon'a red-sensitive silver halide emulsion and superposed thereon a red filter layer, said red filter layer being in contact with said green-sensitive emulsion when the blpack isin operative condition; developing said "blue-sensitive and green-sensitive emulsion layers, removing the silver image formed in these layers by means or a chemical solvent therefor,

exposing said blue-sensitive layer to blue light incident through said first support, developing a yellow image in said blue-sensitive layerwith a color-forming developer, bleaching said-yellow filter layer by means of said solution of sodium hydrosulfite, exposing said green-sensitive layer to blue light, developing this layer with a colorforming developer capable of forming a purple dyestuif, removing the residual silver from said layers, developing said red-sensitive emulsion layer and working :up the sl ilver image thus formed'in any mannerso as to obtain the third picture component.

3. A process of producing color photographs .by the reversal method, which process comprises exposing to light controlled by an object to be photographed at -bi-pack comprising a support, a blue-sensitive silver halide emulsion layer on said support, a filter layer superposed on said layer containing a yellow dyestuii resistant to the photographic treating baths necessary for converting a latent silver image into a positive dyestuiI image, but capable of being deeolorized by a weaksolution of sodium hydrosulfite and sodium carbonate, said solution being incapable of destroying the color-developed dyestuffs and of acting on silver halide, a green-sensitive silver halide emulsion on said filter layer, a second support having cast thereona red-sensitive silver halide emulsion and superposed thereon and filter layer, said red filter layer being in contact with said green-sensitive emulsion when the bi-pack is in operative condition, developing said blue-sensitive and green-sensitive emulsion layers, removing the silver image formed in these layers by means of a chemical solvent therefor, exposing said blue-sensitive layer to blue light incident through said first support, developing a yellow image in said blue-sensitive layer with a color-forming developer, bleaching said yellow filter layer by means of said solution .of sodium hydrosulfite, exposing said green-sensitive layer to blue light, developing this layer with a colorforming developer capable of forming a purple dyestuif, removing the residual silver from said layers, developing said red-sensitive emulsion layer and treating this layer so as to produce a positive blue-green image therein.

4. The process of producing a colored photographic record by color-forming development in a sensitive element having three superposed, differently sensitized silver halide layers, the outer layer of which is sensitized for blue, the inner layer of which is sensitized for red and the intermediate layer of which is sensitized for green,

which comprises forming latent images in the layers, the images being different color sensation records of a subject, processing the film to form light-sensitive silver halide part images in the respective layers, said processing including at least a simultaneous development of said latent images to negative metallic silver images, exposing only one of the layers to visible light of a color to which it is sensitive and developing a colored image in it by a color-forming development step, selectively exposing another layer in visible light of a color to which it is sensitive and developing a colored image in it bya second color-forming development step'and exposing the third layer to visible light of a color to which it is sensitive and developing a colored image in it by a third color-forming development step at least one of said two last mentioned layers being exposed through a previously color de. ve'ioped layer.

5. The process as defined in claim 4 in which silver is removed as a step in the process.

, 6. The process as defined in claim 4, wherein the sensitive element comprises three superposed silver halide emulsions, the outer of which is sensitized to blue, the inner of which is sensitized to red and the intermediate of which is sensitized to green, and in which during color development the dye image produced in each layer is complementary to the' color for which suchlayer is sensitized.

7. The process as defined in claim 4, wherein the successive second exposures are eilected by the utilization between the silver halide layers of filter dyestuiI layers resistant to the photographic treating baths and wherein said filter dyestuff layers are maintained until the color development of at least one of said layers.

8. A process of producing color photographs bythe reversal method, which comprises exposof said solution of sodium hydrosulfite, exposing said green-sensitive layer to blue light, developing this layer with a color-forming developer capable of forming a purple dyestufi, removing the residual silver from said layers, developing mg to light controlled by an object to be photographed a multi-layer material comprising a support, a plurality of silver halide emulsion layers sensitive to three distinct regions of the visible spectrum, said silver halide emulsion layers being combined with a yellow filter layer, comprising azo dyestufi derived from a diazotized arylamine and a pyrazolene, said dyestuif being resistant to the photographic treating baths necessary for converting a latent silver image into a positive dyestufi image, but capable of being decolorized by a weak solution of sodium hydrosulfite, said solution being incapable of destroying the color developed dyestuffs and of acting on silver halide, developing the latent images formed by exposure with an ordinary photographic developer, removing the silver images by means of a chemical solvent for silver, separately exposing at least one of the residual silver halide images to monochromatic light in such a manner that said filter layers confine the action of the light to the particular silver halide image to be exposed, developing said residual silver halide said red-sensitive emulsion layer and working up the silver image thus formed in any manner so as to obtain the third picture component.

10. A process of producing color photographs by the reversal method, which process comprises exposing to light controlled by an object to be photographed a bi-pack comprising a support,

a blue-sensitive silver halide emulsion layer on said support, a filter layer superposed on said layer containing a yellow dyestuif resistant to the photographic treating baths necessary for converting a latent silver image into a positive dyestufl image, but capable of being decolorized by a weak solution ,of sodium hydrosulfite and sodium carbonate, said solution being incapable of destroying the color-developed dyestufls and of acting on silver halide, a green-sensitive silver halide emulsion on said filter layer, a second support having cast thereon a red-sensitive silver halide emulsion, developin said blue-sensitive and green-sensitive emulsion layers, removing the silver image formed in these layers by means, of a chemical solvent therefor, exposing said bluesensitive layer to blue light incident through said first support, developing a yellow image in said blue-sensitive layer with a color-forming developer, bleaching said yellow filter layer by means images thus made developable with a color-forming developer, and destroying the dyestufl in said filter layer by means of said solution or sodium hydrosulflte.

9. A process of producing color photographs by the reversal method, which process comprises exposing to light controlled by.an object to be photographed a bi-pack comprising a support, a 1

blue sensitive silver halide emulsion layer on said support, a' filter layer superposed-on said layer containing a yellow dyestuff resistant to the photographic treating baths necessary for converting a latent silver image into a positive dyestufl image, but capable of being decolorized by a weak solution of sodium hydrosulfite and sodium carbonate, said solution being incapable of destroying the color-developed dyestuffs and of acting on silver halide, a green-sensitive silver halide emulsion on said filter layer, a second supp rt of said solution of sodium hydrosulfite, exposing said green-sensitive layer to blue light, developing'this layer with a color-forming developer capable of forming a purple dyestufi, removin the residual silver from said layers, developing said red-sensitive emulsion layer and treatin this layer so as to produces. positive blue-green image therein.

11. The process. as defined in claim 4 wherein the successive second exposures are efiected by the utilization of filter layers between the silver halide layers, said filter layers comprising azo dyestufis resistant to the photographic treatingbaths necessary for converting a latent silver image into a posttive dyestufl image, but capable of being decolorized by a weak solution of sodium hydrosiflflte, said solution being incapable of destroying the color developed dyestufls and of acting on silver halide.

JOHN EGGERT. BRUNO WENDT. 

